LoongArch: Replace kretprobe with rethook

This is an adaptation of commit f3a112c0c40d ("x86,rethook,kprobes:
Replace kretprobe with rethook on x86") and commit b57c2f124098 ("riscv:
add riscv rethook implementation") to LoongArch. Mainly refer to commit
b57c2f124098 ("riscv: add riscv rethook implementation").

Replaces the kretprobe code with rethook on LoongArch. With this patch,
kretprobe on LoongArch uses the rethook instead of kretprobe specific
trampoline code.

Signed-off-by: Haoran Jiang <jianghaoran@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

1 files changed, 28 insertions, 0 deletions

diff --git a/arch/loongarch/kernel/rethook.c b/arch/loongarch/kernel/rethook.c
new file mode 100644
index 000000000000..db1c5f5024fd
--- /dev/null
+++ b/arch/loongarch/kernel/rethook.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic return hook for LoongArch.
+ */
+
+#include <linux/kprobes.h>
+#include <linux/rethook.h>
+#include "rethook.h"
+
+/* This is called from arch_rethook_trampoline() */
+unsigned long __used arch_rethook_trampoline_callback(struct pt_regs *regs)
+{
+	return rethook_trampoline_handler(regs, 0);
+}
+NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
+
+void arch_rethook_prepare(struct rethook_node *rhn, struct pt_regs *regs, bool mcount)
+{
+	rhn->frame = 0;
+	rhn->ret_addr = regs->regs[1];
+
+	/* replace return addr with trampoline */
+	regs->regs[1] = (unsigned long)arch_rethook_trampoline;
+}
+NOKPROBE_SYMBOL(arch_rethook_prepare);
+
+/* ASM function that handles the rethook must not be probed itself */
+NOKPROBE_SYMBOL(arch_rethook_trampoline);